2.phong has to return the scientific book to thelibrary
=> The scientific book has to be returned to the library by Phong.
3.people must repairthat old building
=> That old building must be repaired.
4.the government will rebuild the memorial monument
=> The memorial monument will be rebulit by the government.
5.the students may elect phong their leader
=> Phong may be elected their leader by the students.
6.the teacher won't accept papers written in pencils
=> Papers written in pencils won't be accepted by the teacher.
7.the athletes might visit some interesting places after sea-games
=> Some interesting places might be visited by the athletes after sea-games.
8.lan's parents have to clean up their house before tet holidays
=> Their house has to be cleaned up by Lan's parent before Tet holidays.
9.the principal might interview her
=> She might be interviewed by the principal.
10.they must keep fruit in the fridge for long
=> Fruit must be kept in the fridge for long.